The present invention encompasses a means for softening fabrics in an automatic dryer. More specifically, certain sorbitan esters, used in combination with certain surfactants, have now been found to be non-staining and useful as dryer-added fabric softeners. The ester-surfactant mixtures herein are conveniently employed in combination with a dispensing means adapted for use in an automatic clothes dryer.
Treatment in an automatic clothes dryer has been shown to be an effective means for imparting desirable tactile properties to fabrics. For example it is becoming common to soften fabrics in clothes dryers rather than during the rinse cycle of a laundering operation.
Fabric "softness" is an expression well-defined in the art and is usually understood to be that quality of the treated fabric whereby its handle or texture is smooth, pliable and fluffy to the touch. Various chemical compounds have long been known to possess the ability to soften fabrics during a laundering or rinsing operation.
The use of fabric softening compounds and compositions designed for application in an automatic dryer has been the subject of recent innovations. Various materials have been suggested for use as dryer-added fabric softeners. In particular, the copending application of Murphy, Diehl, McCarty and Seiden, Ser. No. 461,311, filed Apr. 16, 1974, discloses certain sorbitan esters which are especially suited as dryer-added fabric softeners.
As pointed out in the prior art, many softening agents stain or discolor conditioned fabrics, especially those made with synthetic fibers. This unfortunate staining tendency is apparently caused by the presence of the fatty alkyl groups in the active softening compounds. Thus, the chemical structure which gives rise to the soft, lubricious feel associated with these materials also causes them to be potential fabric stainers.
Heretofore, a variety of mechanical methods have been employed in an attempt to reduce the tendency of dryer-added softeners to stain fabrics. Prior art fabric softening agents have been sorbed into flexible articles which provide controlled release at dryer operating temperatures. Various rigid dispensers and appliances have been designed which assertedly avoid any exceptionally high concentrations of softening agent being undesirably deposited on the fabrics in the form of greasy stains. However, such dispensers are costly and have not come into general use.
The sorbitan ester softeners referred to hereinabove have less of a tendency to stain fabrics than do many of the prior art materials. However, even the sorbitan esters can stain fabrics under certain conditions, e.g., when softening all-polyester fabrics, especially under situations wherein the sorbitan ester is undesirably deposited in gross amounts over a small surface area of the fabric being softened.
It has now been found that, by combining the sorbitan esters with certain phase-modifying agents as hereinafter disclosed, their residual tendency toward staining is suppressed.
The copending application of Murphy and Habermehl, entitled FABRIC TREATMENT COMPOSITIONS, Ser. No. 440,932, filed Feb. 8, 1974, discloses the use of tallowalkyl sulfates to provide controlled, non-staining release of triglyceride fabric softeners from various dispensing means adapted for use in an automatic clothes dryer. In contrast with the triglyceride compositions disclosed in that application which are preferably substantially free from fatty acid soaps, it has now been discovered that soaps are one type of material which are particularly useful in still further reducing the inherently low tendency of the sorbitan esters to stain.
It is an object of the present invention to provide a non-staining means for softening fabrics, especially in an automatic clothes dryer.
Another object herein is to provide articles of manufacture especially adapted for use in an automatic dryer to provide a softness aspect to fabrics without staining.
These and other objects are obtained herein as will be seen from the following disclosure.